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SOUTHFIELD MINE CQAL REFUSE PILE <br />FLOW CAPACITY EVALUATION FOR THE EXISTING UNDERDRAINS <br />In response to Mid-Term Adequacy Comment No. 30, EFCI completed the <br />following analytical evaluation to determine if the two designed <br />underdrains could handle the anticipated flows from the refuse pile. The <br />first objective of this study was to estimate the maximum anticipated <br />inflow from the existing refuse pile. In order to make this estimate <br />EFCI utilized a computerized water balance program developed by the U.S. <br />Army Corps of Engineers for the Environmental Protection Agency (EPA), <br />entitled Hydrological Evaluation of Landfill Performance (HELP). <br />HELP MODEL <br />The model is aquasi-two-dimensional hydrological model of water movement <br />across, into, through, and out of landfills. Although the model was <br />developed with landfills in mind, the concepts and analysis can be applied <br />to any waste pile. <br />• The model accepts climatological, soil, and design data and utilizes a <br />solution technique that accounts for the effects of moisture storage, and <br />lateral drainage. Waste pile systems including various combinations of <br />vegetation, cover soils, waste cells, special drainage layers and <br />relatively impermeable barrier soils. as well as synthetic membrane covers <br />and liners, may be modeled. The program was developed to facilitate rapid <br />estimation of the amount of runoff, drainage, and leachate that may be <br />expected from the operation of a wide variety of waste pile designs. The <br />model is applicable to open, partially closed and fully closed sites. <br />INPUT PARAMETERS <br />The HELP model is set up to utilize standard weather data for a variety of <br />sites across the United States or site specific data. The weather data <br />includes rainfall, snowfall, solar radiation and evapotranspiration. EFCI <br />utilized weather data for Denver which represents a "worst case" assumpton <br />. since precipitation levels are higher and evaporation rates lower for <br />Denver as compared to the mine area. <br />c:~woar~rnn~m~emv u. eev <br />Revised April 1993 <br /> <br />